Synthesis of Natural Products, Carbocycles, and Heterocycles by Hauser–Kraus Annulation
Irishi N. N. Namboothiri, Chenikkayala Siva Sankara, Shweta Prakash Gaikwad
Abstract
Abstract In this Account, we summarize recent developments in Hauser–Kraus (H–K) annulation with respect to syntheses of natural products and other functionalized, fused, or spiro carbocycles and heterocycles. Although the classical H–K annulation occurs between a 1,4-dipolar synthon (a 3-nucleophilic phthalide), and a 1,2-dipolar synthon (a Michael acceptor), alternative modes of annulation, such as [4+4] and [4+1], as well as other reactivities of 3-nucleophilic phthalides that have been reported in recent years, are also covered in this account. 1 Introduction 2 Hauser–Kraus Annulation in Total Syntheses 3 Hauser–Kraus Annulation Methodologies 3.1 [4+2] Annulation 3.2 [4+4] Annulation Followed by Rearrangement 3.3 Michael Addition Followed by E2 Elimination 4 Miscellaneous Reactions 5 Conclusions